How to Write a Demand Letter for an Unpaid Invoice

Follow a clear workflow to demand payment for an overdue invoice and document delivery proof.

Published March 5, 2025

A strong demand letter clarifies what is owed, the deadline to pay, and how the recipient can respond. Use this approach to build a pre-suit record that is easy to follow.

When to use this

A client has not paid after reminders.
You are preparing for small-claims court.
You need a formal request before escalation.

How to do it (fast)

Gather the invoice number, dates, and payment history.
Calculate the total demanded, including late fees if allowed.
Set a deadline date and delivery method.
Send the letter and save proof of delivery.

Why this helps

Clarifies the amount owed and the deadline.
Creates a documented pre-suit demand.
Helps you show delivery proof if the dispute escalates.

Related tools

Not legal advice. Courts set their own rules. Keep your original records.

Keep the letter focused

Stick to the facts: invoice number, dates, amounts, and the deadline. Avoid emotional language so the letter remains professional and easy to review.

Delivery proof matters

Certified mail gives you a delivery record, but email can work if your contract allows it. Save any receipts or confirmation screens.

Draft your demand letter fast

Use the PDF tool to set totals, deadlines, and delivery method details.

Open the demand letter tool

Frequently asked questions

What should I include in a demand letter for an unpaid invoice?

Include invoice identifiers, dates, total amount due, deadline, and payment instructions.

How do I calculate the deadline date?

Count forward 7-14 days from the send date unless your contract requires a different window.

Should I keep proof of delivery?

Yes. Keep certified mail receipts, email confirmations, or screenshots as delivery proof.